Can digital signals from the keyboard capture force exposures during typing?

An exposure-response relationship has been shown between muscle fatigue and its effects on keystroke durations. Since keystroke durations can readily be measured by software programs, the method has the potential as a non-invasive exposure assessment tool. However, the software based keystroke durations may be affected by keyswitch force-displacement characteristics. Thus, this study used a force platform to measure the keystroke durations and compared them to software measured keystroke durations in order to determine whether the software based keystroke durations can be used as a surrogate force exposure measures. A total of 13 subjects (6 males and 7 females) typed for 15 minutes each on three keyboards with different force-displacement characteristics. The results showed that the software based keystroke durations were more sensitive to the keyboard force-displacement differences than the force based measures. Although the digital signal based keystroke durations depend on the force-displacement characteristics, the high correlation between the two measures indicated that the keystroke durations derived from the digital signal approximated the true force derived keystroke durations, regardless of the keyboard force-displacement characteristics. Therefore, the software based keystroke durations could be used as a non-invasive, surrogate force exposure measure in lieu of the more invasive actual force measurements.